1. Technical Field
The present invention relates to a panoramic periscope of the type comprising: a body to be mounted on a vehicle; a head-piece attached to said body and rotating with respect thereto and provided with a window for observing the external scenery; inside said head-piece, a mirror for deflecting the incoming beam from said window towards detection means.
Periscopes of this type are commonly used on various types of vehicles, for example on tanks used in armed combat.
2. Background Art
Examples of panoramic periscopes of this type are described in GB-B-1,272,742, U.S. Pat. No. 3,464,757, U.S. Pat. No. 3,200,250, U.S. Pat. No. 3,549,231 and U.S. Pat. No. 4,108,551.
Depending on the type of use and configuration, the periscope may be provided with an optical path in the visible spectrum, or with an infrared optical path with an associated infrared sensor, or with a laser telemeter, or with a combination of these elements.
The space available in the vehicle where the periscope is installed is restricted and this results in the need for a compact structure. Arranging two or three optical paths (visible, infrared and laser) in a panoramic periscope is difficult since it requires a large amount of space.
Moreover, assembly of the various optical components is complex and delicate, since said components must be mounted and aligned with great precision. This is made difficult owing to the fact that the various components frequently have to be assembled and disassembled. It is required, moreover, to reduce the number of optical components in order to simplify the structure and increase the optical efficiency of the apparatus.
The general object of the present invention is to provide a periscope of the type mentioned above which overcomes the drawbacks of conventional periscopes. In particular, the object of the invention is to provide a periscope which is compact even when two or more optical paths are combined in it. It must also be easy and reliable as regards assembly and adjustment of all its components.
In some configurations of the periscope an infrared viewing module with an I.R. sensor is provided. At present, various types of arrangements of the infrared sensor, or so-called heat chamber, exist in panoramic periscopes. In particular, there exist solutions in which the entire heat chamber and the associated optics are arranged inside the central body of the periscope. This allows perfect alignment of the optics during assembly and avoids risks of misalignment. However, this solution has considerable drawbacks since the periscope body assumes notable proportions with consequent problems of installation and limitations as regards the possibility of combining, with the same periscope, an optical path in the visible spectrum.
When the periscope has a heat chamber for night-time viewing in the infrared range, the present invention has the object of providing a periscope in which joining of the heat chamber to the periscope body can be performed in a particularly simple manner and does not give rise to positioning and alignment problems and which, moreover, is particularly compact and easy to install.
In this context, a further particular object of the present invention is to provide a periscope of the type mentioned above, in which the optical elements along the path of the infrared beam are reduced, so that it is possible to have a more powerful signal.
In some periscopes, a laser telemeter is also provided. In this case a separator element inside the periscope body separates the laser path from the optical path in the visible and/or infrared range. A type of periscope currently known has a separator prism with a dichroic surface oriented so as to deviate the visible beam and allow the laser beam to pass through. The deviated visible beam is reflected onto a side surface of the prism and from here is redirected to a facing side surface from where it emerges so as to be directed towards the viewing module. This separator system has large dimensions and occupies a considerable amount of space inside the periscope body.
Within the scope of the general object of the present invention (i.e. of providing a periscope which is particularly compact and has a small number of optical elements), if the periscope has a laser path, a particular object is that of providing a periscope which has an element for separating the laser beam from the visible beam, which has a particularly limited height, so as to reduce the space occupied inside the periscope body and facilitate, where necessary, the arrangement inside the said periscope body of optics for viewing in the infrared range.
In this context, a further object of the present invention is to provide a periscope in which the separator element allows formation of a visible-beam path, which is more favourable from the point of view of the layout of the device.
Normally the rotating head-piece is mounted on the periscope body by means of a system of supports. The volume of the head-piece is delimited at the bottom by a sealed window, which is transparent for a certain radiation range, for example visible radiation and infrared radiation, so as to allow daytime and night-time viewing. The volume of the central body of the device is in turn closed by a sealed window which is transparent for the same radiation range. Assembly is performed by arranging the two windows facing one another. This therefore results in isolation of the internal volumes of the head-piece and central body from the outside, while the radiation which penetrates into the central body so as to allow viewing directly or via an infrared sensor passes through at least two separation windows.
This has been considered necessary in particular in periscopes with at least two optical paths, because these devices are required to operate in critical environmental conditions and it is necessary to ensure complete isolation, from the outside, of the delicate optical instruments contained in the device. Moreover, the sealing action with respect to the exterior must be ensured so as to prevent escaping of the gas forming the controlled atmosphere inside the device.
However, the presence of two separation windows between the volume of the head-piece and the volume of the body of the device constitutes a serious drawback since it greatly reduces the energy of the beam which reaches the viewing means. This drawback is accentuated in the case of periscopes intended for night-time viewing, since the signal in the infrared range is per se very weak. A loss of signal due to absorption by the two windows constitutes an extremely negative factor in terms of efficiency of the device.
When the periscope must be used for both night-time viewing (by means of infrared images) and daytime viewing (in the visible range) it is necessary to choose a material which is transparent both for radiation in the far infrared range and for visible radiation. The multi-spectral material which can be used in such a wide range of the spectrum reduces the viewing clarity in the visible range, imposing considerable limitations on the overall thickness of the windows.
Moreover, in conventional periscopes, often part of the body of the device is mounted on the vehicle from the inside. If the device is subject to frequent assembly and disassembly operations for reasons of technical maintenance and verification, there is the risk of axial and angular misalignment of the head-piece and body. Such misalignment must be avoided at all costs since, it a sighting grid is provided inside the body of the device, this grid must always be perfectly aligned with the axis of the beam coming from the head-piece. If this condition is not maintained, the device, used for aiming weapons and the like, loses its operational efficiency or the latter is seriously impaired.
In order to avoid these drawbacks, it is necessary to observe very precise tolerances as regards the surfaces for joining together the head-piece and body of the device, with an obvious negative effect in terms of cost.
One particular object of the present invention is to provide a device which allows the signal losses to be reduced, in particular in the far infrared range.
One further particular object of the present invention is to provide a device which eliminates the need for disassembling the head-piece from the body and which therefore eliminates the risk of misalignment between the optics contained in the body and the optics contained in the head-piece, and in particular the misalignment between the sighting grid and the optics of the rotating panoramic head-piece.
A further object of a particular embodiment of the present invention is to provide a device which does not require excessively small machining tolerances as regards the surfaces for joining together the head-piece and body of the device.
Yet another object of an embodiment is that of obtaining a high degree of integration between the components and functions, so as to assembly everything within the space contained in a cylinder and allow assembly of the device from above.
In periscopes of the type currently known, which are provided with an optical path in the visible spectrum for daytime viewing, complex systems for varying the magnification ratio are used. These systems comprise an arrangement of movable optics which change condition depending on the magnification ratio required.
The known devices are costly and delicate, as well as being bulky, a feature which is a particularly unfavourable aspect when the periscope must be installed on vehicles where there are problems of space and robustness, as in the case of tanks used in armed combat.
When the periscope is provided with an optical path in the visible spectrum, a particular object of the present invention is to provide a periscope having a system for changing the magnification ratio which is simpler, more reliable and less bulky than conventional systems.
According to the invention, in order to obtain the advantages and the objects of improved I.R. viewing, the infrared module is joined to the central body in the region of an interface where the infrared beam is collimated. Advantageously it is also possible to envisage that the optics for focussing the infrared beam may comprise a lens defining an exit window of the central body and a lens defining an entry window of the infrared module, for passage of the infrared beam.
In this way the infrared module may be easily disassembled from the periscope body and re-assembled thereon without problems of alignment of the optics contained in the module and in the body respectively, since the collimated beam is insensitive to misalignment of the optical axes, provided that the parallelism of the axes themselves is ensured. This parallelism may be easily obtained by providing two flat reference surfaces, on the module and on the central body of the periscope, respectively. Moreover, if the exit windows of the central body of the periscope and entry windows of the infrared module are defined by lenticular elements of the focussing optics, a further series of advantages is obtained. Firstly, since the lenses constitute at the same time elements for closing and isolating the internal volumes of the central body and the infrared module from the outside, it is possible to avoid inserting into the optical path of the infrared beam further window elements which cause signal loss. This also results in a reduction in the size of the periscope. Moreover, with this configuration at least one lenticular element is present in the central body of the periscope and this makes it possible to align, during assembly, the axis of the incoming beam with the axis of the optics, without the need for introducing auxiliary optical elements for correction of the angle, which would cause loss of energy in the signal.
Moreover, by arranging part of the optics in the central body, while keeping a beam collimated at the interface between central body and infrared module, in the region of this interface there is a section of the beam which is smaller than the section of the incoming beam. This makes is possible to collect in the infrared module all the available energy with a relatively small opening.
According to a particularly advantageous embodiment of the invention, the lens defining the exit window of the central body is mounted on a support, the position of which with respect to the central body is adjustable in a plane perpendicular to the optical axis of the lens itself. This allows easy alignment of the optics during assembly of the device. A similar solution may be adopted for the lens defining the window for entry of the beam into the infrared module.
The focussing optics group housed in the central body of the periscope may consist of a Galilean telescope, the eyepiece of which forms the closing lens of the exit window of the central body. The optics housed in the central body may comprise, moreover, an intermediate optical group movable along the axis of the focussing optics, for modifying the magnification ratio. The intermediate optical group may have associated with it a diaphragm which alternately assumes a displaced position with respect to the optical path, or an active position, in which the diaphragm is positioned along the optical path. In the active position, the diaphragm is positioned between said intermediate optical group and the exit window of the central body.
According to a possible embodiment, the diaphragm is hinged on an axis perpendicular to the optical axis and is biased by a resilient member into its displaced position. The intermediate optical group and said diaphragm have mutually engaging means which cause oscillation of the diaphragm towards its active position when the intermediate optical group performs a translatory movement along the optical axis towards its position furthest from the exit window of the central body, i.e. towards its position adjacent to the objective of the telescope.
Advantageously, the mutually engaging means may comprise a hook integral with the diaphragm, oscillating about the oscillation axis of the diaphragm itself, while the intermediate optical group has a pin which engages in said hook. The shape of the hook and the pin are such that the diaphragm is stabilized in its active position when the intermediate optical group is located approximately in its upper position.
According to a possible embodiment, the infrared module has housed inside it a de-rotator comprising a Pechan prism.
When the periscope has a laser telemeter with a separator element, in order to reduce the space occupied and hence allow integration of the various components, it is envisaged that the separator element may have an entry surface and an exit surface parallel with one another and passed through by said visible optical beam; that the entry and exit surfaces are perpendicular to the visible optical beam; and that the inner dichroic surface is orientated, with respect to the entry surface, so that the laser beam is reflected by the dichroic surface towards the entry surface at an angle such as to be reflected entirely by said entry surface towards a surface for lateral exiting of the laser beam.
A dichroic element of extremely limited thickness is thus obtained, said element being such as to allow assembly in a periscope of small dimensions, or in a restricted zone of a periscope which has, for example, in addition to an optical path in the visible spectrum, also an infrared optical path, while maintaining limited dimensions of the periscope body, for easy installation. The visible beam does not undergo deviations by the separator element and thus allows easier housing of the optics downstream of the separator element.
In order to facilitate formation of the dichroic surface, it is possible to envisage an angle of incidence of the radiation on the dichroic surface which is much smaller than that of conventional devices, for example of the order of 30xc2x0.
In order to reduce the signal losses and facilitate assembly of the head-piece and body of the periscope, when there are at least two optical paths, the head-piece and the entire central body may be stably joined together with the intervening arrangement of a seal which isolates the inside of said head-piece and said body from the outside, allowing mutual rotation.
In this way, the two elements (head-piece and body) may be laboratory-assembled, ensuring once and for all correct alignment of the optical axis of the head-piece and optical elements, in particular the sighting grid, in the periscope body. Assembly and disassembly of the periscope onto and from the vehicle do not require detachment of the head-piece from the body. With the intervening arrangement of a suitable system of gaskets between the head-piece and the body it is possible to eliminate the windows closing off the internal volumes of the head-piece and body, thus eliminating two elements normally present in conventional devices and the cause of a reduction in the signal and hence the efficiency of the periscope, with advantages in particular for night-time infrared viewing, even if there still exists the possibility of retaining only one of these windows, which in this case will have only a mechanical protective, but not a sealing function.
The sealing action may be advantageously obtained by means of the use of a pair of flat and geometrically opposing gaskets, the first of which being designed to ensure sealing from the outside towards the inside and the second of which being designed to ensure sealing from the inside towards the outside. In a practical embodiment, gaskets with a V-shaped section orientated in opposite directions may be used.
In a possible embodiment, the central body of the periscope has been associated with it a viewing module containing means for focussing the beam of visible radiation coming from the panoromic head-piece and at least one eyepiece for observing the external scenery; the viewing module may be separated from the central body in order to facilitate assembly and disassembly of the periscope with respect to the vehicle. In this case the central body and the viewing module have, respectively, an exit window and an entry window for the beam coming from the panoramic head-piece of the periscope. Joining together of the two units (central body and viewing module) may be performed advantageously along flat reference surfaces, perpendicular to the optical axes of the optical elements contained in the units themselves. If, from the last element along the optical path inside the central body, the beam emerges collimated, with this system it is possible to reduce to a minimum the problems of optically joining together the central body and viewing module. In fact, in this case, the system becomes insensitive to any misalignment of the optical axes of the central body and the viewing module, provided that the parallelism thereof is ensured. Said parallelism can be easily obtained with correct and accurate machining of the two flat joining surfaces, which may have a considerable extension in order to ensure the necessary precision.
If the periscope has an optical path in the visible spectrum with a system for changing the magnification ratio, a reduction in the overall dimensions and a greater reliability are obtained with a device in which the means for varying the magnification ratio comprise a movable element carrying an optics group and a reflecting mirror, said movable element being displaceable between two alternative positions: in the first of said positions the reflecting mirror deviates the beam entering the viewing module towards an optical path terminating in the eyepiece or in the pair of eyepieces of the viewing module, whereas the optics carried by the movable element are displaced with respect to the path of the beam; in the second of said positions the reflecting mirror is displaced with respect to the path of the beam and said optics are inserted in the path itself, such that the incoming beam passes through said optics and a series of fixed auxiliary optical elements defining an alternative optical path to the reflecting mirror.
In a practical embodiment, the fixed auxiliary optical elements comprise a convergent lenticular element arranged between two deviating prisms. With this arrangement it is possible to obtain an optical path which forms a quadrilateral, the first side of which defines the entry direction and the second side defines the exit direction of the beam from said alternative optical path, said two entry and exit directions coinciding with the directions of incidence and reelection of the beam on the reflecting mirror, when said reflecting mirror is located in the optical path of the beam.
With the arrangement according to the invention the change in the magnification ratio is obtained with a brief displacement of the movable element carrying the reflecting mirror and the movable optics, while the remaining optics are fixed. This simplifies considerably the structure of the viewing module, allows a reduction in the dimensions thereof and increases the reliability thereof.
So as to allow easy joining together of the viewing module to the central body of the periscope, without the need for imposing a relative coaxial arrangement of the optics present in the body and the optics present in the module, according to a preferred embodiment, the beam incident on the reflecting mirror or entering the movable optics may be a collimated beam.
Further advantageous features of the device according to the invention are indicated in the accompanying claims and described below with reference to an example of embodiment.
The individual contrivances, improvements and innovations summarised above and described in greater detail below may be adopted individually or in various combinations with one another. In particular, the configuration of the I.R. path, the dichroic prism, the mechanism for assembly of the head-piece and body, as well as the means for changing the magnification ratio, may be used independently of one another.